Heat oil in a 12-inch oven-proof heavy skillet over medium-high heat until it shimmers. Brown pork on all sides, about 6 minutes total, then transfer to a plate. Sauté garlic and fennel wedges in skillet until fennel is golden brown, about 6 minutes. Add wine, stirring and scraping up brown bits, then stir in broth and butter. Put pork on top of fennel and transfer skillet to oven. Roast until
an instant-read thermometer inserted into center of pork registers 145 to 150°F, about 15 minutes. Transfer pork to a cutting board and let rest 10 minutes.

Meanwhile, transfer skillet to stovetop (handle will be hot) and boil, stirring occasionally, until most of liquid has evaporated. Stir in lemon juice and 1/4 cup chopped fennel fronds. Thinly slice
pork and serve over fennel with sauce.